1. Field of the Invention
The invention relates generally to a method of forming metal contacts in a semiconductor device, and, more particularly, to a method of removing an anti-reflective coating layer using a high-temperature fluorinated chemistry to provide a semiconductor device having a more consistent planar surface at the conclusion of the metal contact forming step.
2. Description of the Related Art
Anti-reflective coatings have been used in the fabrication of small dimension integrated circuits (ICs) to provide better control over the photolithographic process. In particular, inorganic BARCs (bottom anti-reflective coatings) have been used during the contact hole masking step to reduce the reflections from the underlying topography substrate and thereby provide better control over the width of the photoresist mask openings which are used to form contact holes of a desired width.
FIGS. 1A-1D illustrate a conventional method of forming metal contacts for a semiconductor device in which an anti-reflective coating layer is used to reduce the reflections from the underlying topography substrate. The semiconductor device includes a substrate 10, an active region 15 formed in the substrate 10, an insulating layer 20, which is typically a silicon dioxide (SiO.sub.2) layer, disposed on top of the substrate 10, a BARC layer 30 disposed on top of the insulating layer 20, and a photoresist layer 40 in which mask openings 45 are formed by a conventional photolithographic process.
The semiconductor device illustrated in FIG. 1A is etched to form openings 50 through the BARC layer 30 and the insulating layer 20. FIG. 1B illustrates the semiconductor device having the openings 50 and the photoresist layer 40 removed. On top of the semiconductor device illustrated in FIG. 1B, a metal layer 60, e.g., tungsten (W), is deposited on its surface. The resulting structure is shown in FIG. 1C.
Subsequently, the metal layer 60 is planarized by a conventional polishing process. The metal layer 60 is polished until the entire surface of the BARC layer 30 is exposed and the metal contacts 70 remain. The resulting structure is illustrated in FIG. 1D.
In the conventional method of forming metal contacts, the BARC layer 30 that remains after the metal layer 60 is polished has thickness variations and surface inconsistencies 80 that make post-polish defect inspections extremely difficult. It is thus desirable to provide a semiconductor device having a more consistent planar surface at the conclusion of the metal contact forming step to improve the rate and the quality of post-polish defect inspections.